Natural selection creates tall, short, dark skinned, white skinned humans, but that is not evolution.
No, you're missing it. Natural selection doesn't create tall, short, dark skinned and light skinned. Random mutation does. What natural selection will do is determine which of these traits should carry on to the next generation.
Imagine, hypothetically, that there is some great selection against people of average height. In this situation natural selection favors the short and the tall but eliminates people between say. . . 5'5" and 5'11". Eventually the entire population will either be shorter than 5'5" or taller than 5'11". The two short/tall populations probably won't interbreed much because they will produce average height humans who will be selected against.
Eventually you'll end up with two distinct populations. If enough time passes and they drift far enough away, genetically, then you will end up with two distinct species.
I understand that this is all a hypothetical. However, you must understand that:
1). we don't know the future and can not determine what variation random mutations may provide
2). we don't know the future and can not determine what types of selective pressures there may be
In order for the species to really evolve we must undergo selective pressure that affects our ability to produce offspring. At this point in human history we have enough medical knowledge that not much can affect our ability to produce offspring. Like crocodiles and sharks, we have found a niche that we fit well. There currently isn't much natural selection acting on humans, so there isn't much evolution in our species.
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